1. Technical Field
The technical field relates to a lens actuator, which is used in a camera and a mobile phone.
2. Description of the Related Art
Recently, in a camera and a mobile phone, there has been proposed use of a lens actuator including a shake correction mechanism. The shake correction mechanism mechanically suppresses a vibration of a lens in order to prevent a disturbance of a video image or an image due to a camera shake during shooting.
A conventional lens actuator will be described with reference to FIGS. 5 and 6.
FIG. 5 is a perspective sectional view of conventional lens actuator 20. FIG. 6 is an exploded perspective view of lens actuator 20.
Lens actuator 20 includes movable unit 1, four coil retaining bodies 2A to 2D, lower cover 3, four wires 4, and upper cover 5. In lens actuator 20, movable unit 1 is swung when the camera shake is generated to suppress the disturbance of the video image or the image.
Movable unit 1 includes magnet holder 11, auto focus unit 12 in which the lens moves vertically therein, and imaging body 13.
Eight magnets 14 are fixed to an inside of auto focus unit 12 while arrayed in two upper and lower stages. Four magnets 15, each being slightly larger than magnet 14, are fixed to lateral surfaces on front-back and left-right sides of magnet holder 11.
Auto focus unit 12 includes round hole 12A to which the lens is fixed, and auto focus unit 12 is accommodated inside magnet holder 11. In auto focus unit 12, AF (Auto Focus) coil 16 is disposed opposite magnet 14.
In movable unit 1, a current passed through AF coil 16 generates an electromagnetic force between magnet 14 and AF coil 16, while the lens is allowed to move vertically in auto focus unit 12.
Imaging element 17 is disposed on an upper surface of imaging body 13. Imaging element 17 is a semiconductor element, such as a CCD (Charge Coupled Device) image sensor and a CMOS (Complementary Metal Oxide Semiconductor) image sensor.
Imaging element 17 is disposed below the center of round hole 12A. The vertical movement of the lens can perform auto focus control in which the video image or the image captured by imaging element 17 is automatically brought into focus.
One end of wire 4 is connected to each of four corners of lower cover 3, and the other end is connected to each of four corners in an upper surface of magnet holder 11 of movable unit 1. Wire 4 swingably retains movable unit 1 on lower cover 3.
Generally, a metallic wire having a diameter of 70 μm or more and less than 110 μm is used as wire 4, and movable unit 1 swings with deformation of wire 4. Wire 4 is desirably made of beryllium copper or phosphor bronze.
Coil retaining bodies 2A to 2D are disposed on front-back and left-right sides of movable unit 1. OIS (Optical Image Stabilization) coil 18 is disposed opposite magnet 15.
A current is passed through OIS coil 18 when the camera shake is generated in lens actuator 20. The electromagnetic force generated between OIS coil 18 and magnet 15 swings movable unit 1.
The swing of movable unit 1 performs shake correction control to correct the shake of the video image or the image captured by imaging element 17.